1. Field of the Invention
The present invention relates to window coverings. More particularly, the present spools for horizontal blinds provide an apparatus for winding up multiple lift cords inside a head rail using only one pull cord, wherein the spools reduce the likelihood of the lift cords becoming tangled.
2. Description of the Related Art
Conventional horizontal blinds comprise a plurality of horizontal slats that are raised, lowered and/or rotated to adjust a level of light entering a room through a window or door. The slats are supported from a head rail by ladders. Generally, the blind assembly includes at least two ladders, and may include more ladders depending upon the length or weight of the slats.
Each ladder is typically constructed of a strong fibrous material such as nylon, and comprises a pair of vertically extending uprights supporting a plurality of evenly spaced rungs. An upper end of each upright is secured to a tilting mechanism within the head rail. Lower ends of each upright are secured to a bottom rail. Each rung supports a slat.
The tilting mechanism may comprise an elongate rod having a length substantially equal to a length of the head rail. The rod includes a plurality of attached drums, one drum corresponding to each ladder. Upper ends of the ladder uprights are secured to the drums. A wand or cord descending from the head rail controls rotation of the rod. The drums rotate with the rod, and the ladder uprights follow the rotation of the drums. As the drums rotate in a first direction, the ladder uprights on one side of the slats rise, and the ladder uprights on the opposite side of the slats fall, thus tilting the slats in a first tilt direction. As the drums rotate in a second direction opposite the first direction, the slats tilt in a second tilt direction.
Lifting cords descend from the head rail and are attached at their lower ends to the bottom rail. Generally, a position of each lifting cord along the length of the slats corresponds to a position of a ladder. The lifting cords may be threaded through loops on the ladder uprights, descending along front and back edges of each slat. Alternatively, the lifting cords may pass through apertures in the center of each slat.
The upper end of each lifting cord passes over a pulley within the head rail and attaches to a spool. Preferably, each lifting cord has a unique spool to prevent entanglement of the lifting cords. Generally, each spool includes a portion for winding up a pull cord. The pull cord is connected at its upper end to the spool. The pull cords pass along the head rail to an opening in a lower surface of the head rail. All pull cords pass through this opening and hang freely from the head rail. Free ends of each pull cord are usually secured to one another.
A downward force on the pull cords rotates the spools, unwinding the pull cords from the spools and winding up the lifting cords onto the spools. As the lifting cords wind up, they raise the bottom rail, which in turn raises each successive slat. When the pull cords are released, gravity pulls the bottom rail downward, winding up the pull cords onto the spools, unwinding the lifting cords from the spools, and lowering the bottom rail and slats. A brake positioned within the head rail engages the pull cords at a user's direction. The brake enables the user to selectively control a height of the bottom rail.
Multiple pull cords hanging from the head rail present a strangulation hazard to children. When the blinds are raised, the pull cords descend and often hang such that their lower ends are close to the floor. These dangling cords are attractive to children, and children frequently play with the cords. Unfortunately, these children also frequently become entangled in the cords. Sometimes the cords wrap around a child's neck, the child's airway becomes constricted, and the child dies.
Horizontal blinds having only one pull cord are much safer for children. Although the single dangling pull cord is still an attractive plaything to children, the single cord is much less likely to become wrapped around a child's neck and cause strangulation. Therefore, recent horizontal blind designs include only one pull cord. For example, U.S. Pat. No. 5,799,715 to Biro et al. discloses a Venetian blind assembly 10 including a number of conventional horizontal slats 12. A mechanism within a housing 14 extending across the top of the assembly raises and tilts the slats. Specifically, a pair of lifting cords 16 extend downward from the housing. Each lifting cord extends through a slot 18 in each slat, and through a hole 20 in a bottom rail 22, to a knot 24 at its distal end. The proximal end of each lifting cord extends around a lower surface of a spool 26, into a cord receiving hole 28 through part of a section 30 of the spool. In this way, the lifting cords 16 are simultaneously wound or unwound on the spool with rotation of the spool.
The spool rotates in response to motion of a pull cord 32, which extends from the lower surface of the spool opposite the direction in which the lifting cords extend. Thus, pulling the pull cord downward causes the pull cord to be unwound from the spool as the lifting cords are wound onto the spool. As the lifting cords wind onto the spool, the bottom rail rises. Similarly, releasing the pull cord causes the bottom rail to descend under the influence of gravity. As the bottom rail descends, the pull cord winds onto the spool and the lifting cords unwind from the spool. A conventional braking mechanism 34 releasably engages the pull cord, enabling the bottom rail to be suspended at any point in its vertical travel.
Means are also provided for guiding up to four lifting cords into and out of four sections of the spool. To prevent tangling of the lifting cords with one another, each section winds up only one lifting cord. Thus, the sections are separated from one another, and from a section 64, on which the pull cord is wound, by intervening flanges 66. A guiding structure 68 provides five channels 70 to direct the passage of the lifting cords through a flange 72 of a spool bracket 62. Each channel 70, being in a proximate relationship with an associated spool section, aligns a lifting cord with the section on which it is wound. Feeding each lifting cord centrally onto a spool section eliminates a tendency of the cord to build up windings along a flange.
The lifting cords of the Venetian blind assembly of Biro tend to bunch up on the lifting cord spool. The cords do not wind up in a predictable manner, but rather wind up in a random haphazard way. As a result, each cord tends to become tangled with itself. When the cords become tangled, they prevent the bottom rail from raising and lowering smoothly. To untangle the cords, a user must disassemble the head rail, which is a time consuming process.
The configuration of Biro also limits the capacity of each lifting cord spool section to accept lifting cords. As the width of each section increases, so does its capacity to accept lifting cords. However, the lifting cord spool sections of Biro are all mounted side-by-side and coaxially on a single spool. Thus, the maximum width of each section, and each section's lifting cord capacity is limited by the front-to-back width of the housing.
Therefore, new spools for horizontal blinds that reduce any tendency of the lifting cords to become tangled, and that increase the lifting cord capacity of the spools, would be of great benefit to users of horizontal blinds.